Android: Setup Appbuilder being called multiple times

[marcussacana]

The bug
When the app isn't entire closed, if we try open the app again, the Avalonia Activity OnCreate method is triggered again and causes the problem.

To Reproduce

1. Start your application
2. "Exit" pressing "Back" (That should keep the app running in background)
3. Try return to your app without close it
4. Throws this error:

System.InvalidOperationException: Setup was already called on one of AppBuilder instances
   at Avalonia.Controls.AppBuilderBase`1[[Avalonia.AppBuilder, Avalonia.PlatformSupport, Version=0.10.999.0, Culture=neutral, PublicKeyToken=c8d484a7012f9a8b]].Setup() in /_/src/Avalonia.Controls/AppBuilderBase.cs:line 302
   at Avalonia.Controls.AppBuilderBase`1[[Avalonia.AppBuilder, Avalonia.PlatformSupport, Version=0.10.999.0, Culture=neutral, PublicKeyToken=c8d484a7012f9a8b]].SetupWithLifetime(IApplicationLifetime lifetime) in /_/src/Avalonia.Controls/AppBuilderBase.cs:line 179
   at Avalonia.Android.AvaloniaActivity`1[[Sample.App, Sample, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].OnCreate(Bundle savedInstanceState) in /_/src/Android/Avalonia.Android/AvaloniaActivity.cs:line 52
   at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_(IntPtr jnienv, IntPtr native__this, IntPtr native_savedInstanceState)
   at Android.Runtime.JNINativeWrapper.Wrap_JniMarshal_PPL_V(_JniMarshal_PPL_V callback, IntPtr jnienv, IntPtr klazz, IntPtr p0)

• OS: Android 10
• Version 0.10.15 + 0.10.999-cibuild0019213-beta

[marcussacana]

I forgot, but my stock phone ROM is infamous for causing bugs because of the aggressive battery optimization.
I don't have another phone to test it, then maybe my issue may be invalid.

[kekekeks]

@maxkatz6 I think we should

1. move AppBuilder initialization from AvaloniaActivity to a separate AvaloniaMainActivity class
2. have some static fields in said class to initialize only once and keep Content alive between instances

[maxkatz6]

have some static fields in said class to initialize only once and keep Content alive between instances

AndroidX with android-viewmodel sharing was added for that matter before. See #7435

But I think we can move it to the separated activity and remove androidx from dependencies list.

[maxkatz6]

@marcussacana I can reproduce it as well, so most likely not related to your phone

[marcussacana]

thx guys!